An electromyogram (EMG) measures the electrical activity of muscles when they're at rest and when they're being used. Nerve conduction studies measure how well and how fast the nerves can send electrical signals.

Nerves control the muscles in the body with electrical signals called impulses. These impulses make the muscles react in certain ways. Nerve and muscle problems cause the muscles to react in ways that aren't normal.

If you have leg pain or numbness, you may have these tests to find out which nerves are being affected and how much they are affected. These tests check how well your spinal nerves are working. They also check the nerves in your arms and legs.